Concentration measuring method

ABSTRACT

To provide a concentration measurement method that makes it possible to accurately, quickly, and non-destructively measure the concentration of a predetermined chemical component to a trace level of concentration by a simple means, that makes it possible to accurately and quickly measure the concentration of a chemical component within an object to be measured to a nano-order trace concentration level in real time, and that has a versatility which makes it possible to adapt said concentration measurement method to a variety of situations and embodiments. A time sharing method is used to irradiate an object to be measured with each of light of a first wavelength and light of a second wavelength having different light absorption rates with respect to the object to be measured, light of each of said wavelengths that arrives optically through the object to be measured as a result of irradiating with the light of each of said wavelengths is received by a shared light reception sensor, a signal relating to light of the first wavelength and a signal relating to light of the second wavelength are output from the light reception sensor in accordance with the received light and a differential signal of said signals is formed, and the concentration of a chemical component in the object to be measured is derived on the basis of the differential signal.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a concentration measuring methodrelated to a concentration of a predetermined chemical component in aliquid or a gas, a sugar content in a fruit or a vegetable, a sake metervalue (sweetness/dryness) of Japanese sake, or the like.

Description of the Background Art

In the manufacture of a semiconductor, mixed gases are often suppliedfrom the same line inside a treatment chamber of a semiconductormanufacturing device. The supply of such a mixed gas requires that amixture ratio of component gases be kept constant during the treatmentprocess period, and instantaneously changed as intended. To this end, aflow rate control device, such as a flow control system component(FCSC), for example, that comprises a gas flow rate measurementmechanism and a gas flow rate adjustment mechanism is arranged in thegas supply line. In this FCSC, the degree to which the flow rate perunit time (hereinafter also referred to as “unit flow rate”) of eachcomponent gas that constitutes the mixed gas can be accurately measuredis important.

Today, in a semiconductor manufacturing process in which there are manyopportunities to implement a treatment process such as film formation oretching at an atomic- to nano-order level, the unit flow rate of eachcomponent gas in a mixed gas immediately prior to introduction to atreatment chamber needs to be measured accurately and instantaneouslydown to a range of a small amount.

In such a conventional flow rate control device that satisfies therequirement described above, generally the flow rate of each singlecomponent gas prior to mixture is measured and the target mixture ratioof the mixed gas is calculated from the measured flow rate values.

Nevertheless, the mixture ratio of the mixed gas at the moment ofintroduction into the treatment chamber (hereinafter also referred to as“actual mixture ratio”) is not always guaranteed to be the same as themixture ratio calculated from the measured flow rate values (hereinafteralso referred to as “measured mixture ratio”) during process execution.Thus, conventionally a feedback mechanism is provided that measures theflow rate of each single component gas either continually or at apredetermined interval, and adjusts each of the flow rates so that, whenthe flow rate of any single component gases fluctuates, the mixtureratio becomes the original predetermined mixture ratio based on the newvalue (Patent Document 1, for example).

On the other hand, examples of a gas concentration measuring systeminclude a system that uses a partial pressure measurement sensor thatmeasures the partial pressure of a material gas by a non-dispersiveinfrared absorption method, and calculates the concentration of thematerial gas on the basis of the partial pressure measurement value ofthis sensor by a mathematical operation (Patent Document 2, forexample).[0006]

Further, in metal-organic compound chemical vapor deposition (MOCVD;chemical vapor deposition that uses a metal-organic compound) as well,formation of a uniform film requires control of the suppliedconcentration of the metal-organic compound so that the suppliedconcentration of the metal-organic compound is constant during the filmformation process period, or so that the supplied concentrationfluctuates in accordance with the component distribution of themetal-organic compound to ensure formation of a film with a preferredcomponent distribution. Generally, the metal-organic compound is mixedinto a carrier gas via bubbling or the like, and supplied to thetreatment chamber. The used metal-organic compound is not limited to asingle compound, and a plurality of compounds may be used as well.Examples of the method used to supply the raw material gases of aplurality of types of metal-organic compounds in accordance with designvalues include a method for using infrared gas analysis means (PatentDocument 3, for example).

Furthermore, in the field of fruit and vegetable production and shippingas well, measurement of the concentration of a component such as asweetness component of the fruit or vegetable is important indetermining the sales price of the fruit or vegetable to be shipped.That is, the sweetness of a fruit or vegetable such as an apple, pear,peach, persimmon, strawberry, or watermelon significantly affects thesales price of the product, and thus knowing whether or not thesweetness is ideal for harvest for shipping is a matter of keen interestto the fruit and vegetable producer. One method for ascertaining thesweetness of a fruit or vegetable is to measure the sugar content in thefruit or vegetable in a non-contact manner using infrared light (PatentDocument 4, for example).

Further, medically related, the ability to instantaneously measure bloodcomponents in the bloodstream, for example, such as the red blood cellcount, white blood cell count, platelet count, reticulocyte count, andhemoglobin level in a living body in a non-contact (non-destructive,non-invasive) manner without drawing blood would not only alleviate theburden of the patient but also mentally and physically alleviate thelabor burden of doctors, nurses, and medical technicians. Thus, theability to easily and instantaneously take such measurements in a livingbody in a non-contact, non-invasive manner has been desired. Forexample, recently the number of diabetes patients in youngerdemographics is on the rise, increasing the demand for test methods thatallow tests to be conducted easily, quickly, and with high accuracy.Furthermore, not only are there many patients under doctor care, butthere are many latent patients (potential patients) as well, and thenumber of cases in which, for example, such a patient experiences asudden drop in blood sugar level while driving, fully or partially losesconsciousness, and causes an accident is increasing daily. While theconcentration of glucose (blood sugar level, blood sugar) in the bloodis normally continually adjusted within a certain range by the activityof various hormones (insulin, glucagon, cortisol, and the like), whenthis adjustment mechanism fails for any of a variety of reasons, theamount of sugar in the blood increases abnormally, resulting indiabetes. Diabetes is a disease that refers to a condition in which theblood sugar level (concentration of glucose in the blood) is abnormallyhigh, and is diagnosed when the blood sugar level or hemoglobin Alecvalue exceeds a certain standard. Diabetes may cause symptomsattributable to the high blood sugar itself and also, over time,glycation in which glucose, having a high concentration in the blood,binds with protein in the vascular endothelium due to the highreactivity of the aldehyde group, resulting in the gradual destructionof microvessels in the body, causing serious disorders(microangiopathies including diabetic neuropathy, diabetic retinopathy,and diabetic nephropathy) in various organs in the body, including theeyes and kidneys (complications). Thus, appropriate blood sugarmanagement is important in the treatment of diabetes, includingcontinual strict blood sugar control, medical diet and therapeuticexercise review, insulin dose adjustment and review,verification/prediction of low blood sugar by medical treatment,alleviation of low blood sugar anxiety, and avoidance of severehyperglycemia.

Measurement of blood sugar level in medical institutions such ashospitals is generally performed by a so-called invasive method fordrawing blood from a finger, arm, or the like of the living body.Further, diabetes patients are tested for blood sugar level duringtreatment under the care of a physician in the hospital. On the otherhand, in many cases the blood sugar level needs to be measured daily,and thus a patient must often perform blood sugar level measurements onhis or her own using a self-monitoring of blood glucose (SMBG) device ina hospital bed or at home. While measurement has become rather simple,blood still must be drawn either by the patient or with the help ofanother. Blood is drawn by puncturing a finger or an arm. Thispuncturing is associated with pain and a puncture wound, placingphysical and mental stress on the patient. While recently the use of apainless needle may be considered, association with a puncture woundcannot be avoided, and health safeguards for preventing infection causedby open wounds and the like are required. Recently, as a solution tothis problem, non-invasive methods are proposed (Patent Documents 5 and6, for example).

On the other hand, in Japan, both the blood sugar level and thehemoglobin Alec value must be measured to assess diabetes. Examples ofmethods for measuring both the blood sugar level and the hemoglobin A1cvalue include the method set forth in Patent Document 7.

Furthermore, a method that allows measurement of a sake meter value(hereinafter “SMV”), acidity, and amino acidity in the manufacturingprocess of Japanese sake, with high accuracy, promptness, and a simpleconfiguration, has been in demand. Japanese sake is a liquor delicate inflavor and aroma. Japanese sake is gauged in terms of sweetness/drynessby its SMV, and in terms of full-bodied/light flavor by its acidity. TheSMV refers to the amount of sugar and acid dissolved in the sake, and isa unit that expresses the specific gravity of the refined sake. The SMVis measured by bringing the temperature of the sake to be measured to15° C., and then floating a hydrometer called an SMV meter in the sake.Japanese sake having the same weight as distilled water at 4° C. isgiven an SMV of “0.” Any lighter sake is indicated by a positive (+)value, and any heavier sake is indicated by a negative (−) value. InJapanese sake, what determines sweetness is glucose concentration.

In contrast to SMV which gauges sweetness/dryness, acidity (level oflight/full-bodied flavor) gauges richness and depth. A Japanese sakewith a higher acidity has a more full-bodied flavor, while a Japanesesake with a lower acidity has a lighter flavor. Given the same SMV, aJapanese sake with a high acidity is spicier while a sake with a lowacidity is sweeter. Conversely, a Japanese sake with low acidity tendsto lack a smooth, clean finish, and have a shallow flavor. This acidity,however, affects not only richness, but the actual sweet/spicy flavor aswell. In general, a higher acidity tends to result in a spicier taste.Conversely, a low acidity results in a sweeter taste, even if the sugarcontent is not high. Acidity is measured by the number of titrationmillimeters of a 1/10 normal sodium hydroxide solution that is requiredto neutralize 10 milliliters of the refined sake. If this value is high,expressions such as “plain” are used. If this value is low, expressionssuch as “rich” are used. Further, with Japanese sake, amino acidity(tastiness) is also important. Amino acids are elements that bringsavoriness, and high amino acidity results in an increase in savoryelements, and thus a rich sake flavor. However, savoriness does notnecessarily increase as the amino acidity is increased, resulting in anoff-flavor when too high.

As described above, in the manufacture of Japanese sake, the managementof SMV, acidity, and amino acidity significantly affects the businessvalue (hereinafter also referred to as “sales value”) of themanufactured sake. The SMV, acidity, and amino acidity sensitivelyfluctuate according to humidity, temperature, and sanitary aspects, andthus humidity, temperature, and sanitary aspects are strictly controlledin the manufacture of Japanese sake and SMV, acidity, and amino acidityare frequently measured in the manufacturing process.

PATENT DOCUMENTS

-   Patent Document 1: Japanese Laid-Open Patent Application No.    2012-138407-   Patent Document 2: Japanese Laid-Open Patent Application No.    2010-109304-   Patent Document 3: Japanese Laid-Open Patent Application No.    2006-324532-   Patent Document 4: Japanese Laid-Open Patent Application No.    2003-114191-   Patent Document 5: Japanese Laid-Open Patent Application No.    2008-256398-   Patent Document 6: Japanese Laid-Open Patent Application No.    2006-141712-   Patent Document 7: Japanese Laid-Open Patent Application No.    2012-137500

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In the concentration measuring method or concentration adjustment methodset forth in each of the patent documents described above, problems suchas the following exist.

In Patent Document 1, the flow rate is measured on an upstream side ofthe treatment chamber and merely fed back, and thus the problem ofwhether or not the measured mixture ratio and actual mixture ratio areidentical remains unresolved. Furthermore, while the length of thesupply line from the mixing position to the position of introductioninto the treatment chamber needs to be adequately set to ensure that themixed state of the gases is uniform, doing so makes it all the moredifficult to regard the measured mixture ratio and actual mixture ratioas identical. To ensure that the measured mixture ratio and the actualmixture ratio are identical, one may consider positioning the mixingposition and the introduction position as close to each other aspossible, but doing so results in the problem that it is difficult toguarantee a uniform mixture. Attempting to resolve such problems inaddition to the problems described above results in an increasinglycomplex mechanism, and requires rather advanced control technology.Additionally, according to the configuration of Patent Document 1,measurement is performed by flow rate measurement, and thus gases cannotbe specified.

In the case of Patent Document 2, measurement is performed by partialpressure measurement and thus the method is unsuitable for such highaccuracy measurement as addressed here. Furthermore, the measurementerror undeniably increases when the partial pressure measurement isperformed in a range of an extremely small order.

The method disclosed in Patent Document 3 is configured to individuallyadjust any one of first infrared gas analysis means for measuring theconcentration of each raw material gas in a mixed gas supplied from agas mixing chamber to a reaction chamber, second infrared gas analysismeans for measuring a concentration of each raw material gas in adischarged gas discharged from the reaction chamber, the flow ratecontrol means for calculating an amount of consumption of each rawmaterial gas inside the reaction chamber based on the measurementresults of the first and second infrared gas analysis means and settingthe difference between the calculated value and a predetermined designvalue as a control amount, a gas supply source temperature control unit,and a substrate temperature control unit. Thus, the raw material gasesconsumed not by film formation but by an inner wall surface of thereaction chamber and the like are not taken into consideration, makingit difficult to form a thin film having a uniform film thickness anduniform components. Moreover, a specific example of the infrared gasanalysis means is not illustrated in Patent Document 3. As a result,while formation of a thin film having uniform components and a uniformfilm thickness at the nano-order level requires strict control of thesupplied concentration of the metal-organic compound in order to supplythe metal-organic compound to the treatment chamber at a predeterminedconcentration for a certain period of time, demanding high accuracy inconcentration measurement, this demand is not simply satisfied.

The method set forth in Patent Document 4 irradiates two monochromaticlights having different wavelengths onto a fruit or a vegetable,determines each coefficient of an identification formula from values oflight transmittances Ta, Tb of a plurality of actual measurementexamples in relation to each monochromatic light and values of a sugarcontent C of actual measurements of the examples, and uses the data ofeach determined coefficient as well as the measured light transmittancesof the two monochromatic lights to find the sugar content using theidentification formula. This method, therefore, merely finds the averagesugar content of the fruit or vegetable subjected to sugar contentmeasurement. Thus, in the case of a fruit or a vegetable having a highsugar content near the peel or core, it may be difficult to avoidinclusion of a fruit or a vegetable that has an inadequate sugar contentdepending on the section consumed and thus decreases product price in ashipment.

In the methods of Patent Documents 5 and 6, measurement errorsattributable to patient nervousness and perspiration in the affectedmeasurement region or a rise in body temperature cannot be avoided.Measurement methods of a blood sugar measuring device include enzymeelectrode methods and enzyme colorimetric (colorimetric determination)methods. Enzyme electrode methods include glucose oxidase (GOD) methodsand glucose dehydrogenase (GDH) methods. Enzyme colorimetric(colorimetric determination) methods include hexokinase (HX) methods andglucose oxidase/peroxidase (GOD/POD) methods. However, while errors arenot evident in the measurement value of each device, when a hematocrit(a test for checking the percentage of red blood cells in a given sampleof blood) value is between 20% and approximately 60%, the problem arisesthat the methods indicate a high value for blood having a hematocritvalue below 20%, such as in patients with severe anemia or dialysispatients, and conversely a low value for hypervolemic blood having ahematocrit value above 55%, such as in newborns and in women prior tomenstruation. Thus, the methods are inappropriate for patients withsevere anemia and dialysis patients. Furthermore, GOD methods areproblematic in that the measured blood sugar level decreases to theextent that the partial pressure of the dissolved oxygen in the blood ishigh. Thus, GOD methods are not appropriate for patients that use oxygenfor breathing control. In addition, a normal measurement value may notbe obtained for reasons attributable to verification of blood drawingand blood dotting procedures, how the test paper is attached, how themeasurement device is used, and the like.

The method set forth in Patent Document 7 takes measurements using thesame measurement principle of detecting coloring from hemoglobin,coloring from saccharized hemoglobin, and coloring from glucose byreflecting light having different wavelengths. While offering theadvantages of simplifying and reducing the size of the device, themethod requires a reagent and coloring work for three types of coloring,i.e., hemoglobin, saccharized hemoglobin, and glucose, and also comeswith the burden of drawing blood.

Further, while humidity, temperature, and sanitary aspects are strictlycontrolled in the manufacture of Japanese sake, and SMV, acidity, andamino acidity are frequently measured in the manufacturing process, amethod for measuring SMV, acidity, and amino acidity quickly andaccurately down to a concentration range of an extremely small amount ina non-destructive manner using simple means has not yet been provided.

As understood from the above description, a concentration measuringmethod that allows quick and accurate measurement of a concentration ofa predetermined chemical component down to a concentration range of anextremely small amount in a non-destructive manner using simple meanshas not yet been provided.

Further, a concentration measuring method that allows measurement of theconcentrations of a plurality of chemical components in an object to bemeasured with high accuracy in real time using the same measurementsystem and the same conditions, regardless if the component is a gas, aliquid, or a solid, has not yet been provided.

Furthermore, a concentration measuring method that allows quick andaccurate measurement of the concentration of a chemical component in anobject to be measured down to a concentration range of an extremelysmall amount in the nano order in real time, the method havinguniversality, i.e., the ability to be embodied in various forms andmodes, has not yet been provided.

Furthermore, a concentration measuring method that allows quick andaccurate measurement of the concentrations of a plurality of chemicalcomponents in an object to be measured in real time using a simpleconfiguration has not yet been provided.

The present invention was achieved as a result of close research on thepoints described above.

It is therefore an object of the present invention to provide aconcentration measuring method that allows quick and accuratemeasurement of a concentration of a chemical component in real time,using a simple configuration.

Another object of the present invention is to provide a concentrationmeasuring method that allows quick and accurate measurement of aconcentration of a chemical component in an object to be measured, downto a concentration range of an extremely small amount in the nano orderin real time using a simple configuration, regardless if the componentis a gas, a liquid, or a solid, the method having universality, i.e.,the ability to be embodied in various forms and modes.

Yet another object of the present invention is to provide aconcentration measuring method that allows quick and accuratemeasurement of a concentration of a chemical component in anon-destructive, non-contact manner, down to a range of an extremelysmall amount using a simple configuration.

Yet another object of the present invention is to provide aconcentration measuring method that allows measurement of aconcentration of a chemical component, down to a range of an extremelysmall amount with measurement errors based on environmental fluctuationsand characteristic fluctuations in system components, such as electricalcircuits or electronic elements, eliminated at least to the extentsubstantially possible.

Yet another object of the present invention is to provide aconcentration measuring method that allows measurement of a blood sugarlevel in a non-invasive manner using a simple configuration and methodin a state that is at least substantially free of measurement errorsattributable to patient nervousness and perspiration in the affectedmeasurement region or a rise in body temperature (errors based on thephysiological state of a specimen or an object to be measured;hereinafter also referred to as “physiological errors”).

Yet another object of the present invention is to provide aconcentration measuring method that allows quick and accuratemeasurement of concentrations of a plurality of chemical components inan object to be measured in real time, using a simple configuration.

Yet another object of the present invention is to provide aconcentration measuring method that allows simple and easy measurementof both a blood sugar level and a hemoglobin A1c value using the sameconfiguration and method.

Means for Solving the Problems

A first aspect of the present invention is a concentration measuringmethod for optically measuring a concentration of a predeterminedchemical component in an object to be measured, the method comprisingthe steps of:

irradiating at least light (1) having a first wavelength (λ1) that hasan absorbability with respect to the chemical component, and light (2)having a second wavelength (λ2) that has no or substantially noabsorbability with respect to the chemical component, or anabsorbability that is relatively lower than that of the light having thefirst wavelength, from light-emitting means toward the object to bemeasured using a time-sharing method;sequentially receiving the light that is produced by the irradiation andpasses through the object to be measured by light-receiving means;inputting a first light-receiving signal (1) based on the light (1) anda second light-receiving signal (2) based on the light (2), eachproduced by the received light into differential signal forming means;deriving the concentration of the predetermined chemical component froma measured value based on a differential signal output from thedifferential signal forming means in accordance with the input, and datastored in storage means in advance; andfeeding back a feedback signal corresponding to the differential signalto light emission amount control means for controlling a light emissionamount of the light-emitting means and/or the differential signalforming means.

A second aspect of the present invention is a concentration measuringmethod for optically measuring a concentration of a predeterminedchemical component in an object to be measured, the method comprisingthe steps of:

irradiating at least light having a first wavelength that has anabsorbability with respect to the chemical component, and light having asecond wavelength that has no or substantially no absorbability withrespect to the chemical component, or an absorbability that isrelatively lower than that of the light having the first wavelength,from a single light-emitting means toward the object to be measuredusing a time-sharing method;sequentially receiving the light that is produced by the irradiation andpasses through the object to be measured in a time-sharing manner by asingle light-receiving means;inputting a first light-receiving signal based on the light having thefirst wavelength and a second light-receiving signal based on the lighthaving the second wavelength, each produced by the received light, intodifferential signal forming means;deriving the concentration of the predetermined chemical component froma measured value based on an output signal output from the differentialsignal forming means in accordance with the input, and data stored instorage means in advance; andcontrolling a light emission amount of the light-emitting means on thebasis of a feedback signal corresponding to the differential signal.

A third aspect of the present invention is a concentration measuringmethod comprising the steps of: irradiating at least light having afirst wavelength and light having a second wavelength, each having adifferent light absorptivity with respect to an object to be measured,onto the object to be measured using a time-sharing method;

sequentially receiving the light of each wavelength that opticallypasses through the object to be measured as a result of the irradiationof the light of each wavelength, using a common light-receiving sensor;forming a differential signal between a signal related to the lighthaving the first wavelength and a signal related to the light having thesecond wavelength output from the light-receiving sensor in accordancewith the received light;deriving a concentration of a chemical component in the object to bemeasured on the basis of the differential signal; andcontrolling the amount of light during the emission of at least one ofthe light having the first wavelength and the light having the secondwavelength on the basis of a feedback signal corresponding to thedifferential signal.

A fourth aspect of the present invention is a concentration measuringmethod comprising the steps of: irradiating a first light and a secondlight, each having a different light absorptivity with respect to anobject to be measured, onto the object to be measured using atime-sharing method; receiving each light that optically passes throughthe object to be measured by irradiation of each light onto the objectto be measured, using a common light-receiving sensor;

forming a differential signal on the basis of a signal related to thefirst light and a signal related to the second light output from thelight-receiving sensor in accordance with the received light; deriving aconcentration of a predetermined chemical component in the object to bemeasured on the basis of the differential signal; andcontrolling the amount of light during the emission of at least one ofthe light having the first wavelength and the light having the secondwavelength on the basis of a feedback signal corresponding to thedifferential signal.

A fifth aspect of the present invention is a concentration measuringmethod comprising the steps of: irradiating at least light having afirst wavelength and light having a second wavelength, each having adifferent light absorptivity with respect to an object to be measured,onto the object to be measured using a time-sharing method;

receiving the light of each wavelength that optically passes through theobject to be measured as a result of the irradiation of the light ofeach wavelength, using a common light-receiving sensor;forming a differential signal between a signal related to the lighthaving the first wavelength and a signal related to the light having thesecond wavelength output from the light-receiving sensor in accordancewith the received light;deriving a concentration of a chemical component in the object to bemeasured on the basis of the differential signal; andcontrolling the amount of light during the emission of at least one ofthe light having the first wavelength and the light having the secondwavelength on the basis of a feedback signal corresponding to thedifferential signal.

A sixth aspect of the present invention is a concentration measuringmethod comprising the steps of: irradiating at least a first light and asecond light, each having a different light absorptivity with respect toan object to be measured, onto the object to be measured using atime-sharing method; receiving each light that optically passes throughthe object to be measured by irradiation of each light onto the objectto be measured, using a common light-receiving sensor;

forming a differential signal on the basis of a signal related to thefirst light and a signal related to the second light output from thelight-receiving sensor in accordance with the received light; deriving aconcentration of a predetermined chemical component in the object to bemeasured on the basis of the differential signal; andcontrolling the amount of light during the emission of at least one ofthe light having the first wavelength and the light having the secondwavelength on the basis of a feedback signal corresponding to thedifferential signal.

A seventh aspect of the present invention is a concentration measuringmethod for optically measuring a concentration of a predeterminedchemical component in an object to be measured, the method comprisingthe steps of irradiating at least light having a first wavelength thathas an absorbability with respect to the chemical component, and lighthaving a second wavelength that has no or substantially no absorbabilitywith respect to the chemical component or an absorbability that isrelatively lower than that of the light having the first wavelength froma single light-emitting means toward the object to be measured using atime-sharing method, receiving the light produced by the irradiationfrom the object to be measured by a single light-receiving means,inputting a first light-receiving signal based on the light having thefirst wavelength and a second light-receiving signal based on the lighthaving the second wavelength, each produced by the received light, intoa differential circuit, comparing a measured value based on an outputsignal output from the differential circuit in accordance with the inputwith data stored in advance in storage means, and deriving theconcentration of the predetermined chemical component accordingly.

An eighth aspect of the present invention is a concentration measuringmethod comprising the steps of irradiating at least light having a firstwavelength and light having a second wavelength, each having a differentlight absorptivity with respect to an object to be measured, onto theobject to be measured using a time-sharing method, receiving the lightof each wavelength that optically passes through the object to bemeasured as a result of the irradiation of the light of each wavelengthusing a common light-receiving sensor, forming a differential signalbetween a signal related to the light having the first wavelength and asignal related to the light having the second wavelength output from thelight-receiving sensor in accordance with the received light; andderiving a concentration of a chemical component in the object to bemeasured on the basis of the differential signal.

A ninth aspect of the present invention is a concentration measuringmethod comprising the steps of irradiating at least a first light and asecond light, each having a different light absorptivity with respect toan object to be measured, onto the object to be measured using atime-sharing method, receiving each light that optically passes throughthe object to be measured by irradiation of each light onto the objectto be measured using a common light-receiving sensor, forming adifferential signal on the basis of a signal related to the first lightand a signal related to the second light output from the light-receivingsensor in accordance with the received light, and deriving aconcentration of a predetermined chemical component in the object to bemeasured on the basis of the differential signal.

Effect of the Invention

According to the present invention, it is possible to measure aconcentration of a predetermined chemical component quickly andaccurately in a non-destructive manner down to a concentration range ofan extremely small amount using simple means.

Further, it is possible to measure with high accuracy the concentrationsof a plurality of chemical components in an object to be measured inreal time using the same measurement system and the same conditions,regardless if the component is a gas, a liquid, or a solid.

Furthermore, it is possible to provide a concentration measuring methodthat allows quick and accurate measurement of a concentration of achemical component in an object to be measured, down to a concentrationrange of an extremely small amount in the nano order in real time, themethod having universality, i.e., the ability to be embodied in variousforms and modes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a timing chart for explaining the principles of aconcentration measuring method of the present invention.

FIG. 2 is a block diagram for explaining a configuration of a preferredembodiment of an optical concentration measuring system that embodiesthe concentration measuring method of the present invention.

FIG. 3 is a flowchart for explaining a preferred embodiment of theconcentration measuring method of the present invention.

FIG. 4 is a timing chart for explaining a signal output timing of theexample in FIG. 3.

FIG. 5 is a flowchart for finding an analytical curve.

FIG. 6 is a graph of a relationship between a gas concentration GC and“−log (1−ΔT).”

FIG. 7 is an explanatory schematic configuration view for explainingmain components of a preferred embodiment of the optical concentrationmeasuring system that embodies the concentration measuring method of thepresent invention.

FIG. 8 is an explanatory schematic configuration view for explainingmain components of another preferred embodiment of the opticalconcentration measuring system that embodies the concentration measuringmethod of the present invention.

FIG. 9 is an explanatory schematic configuration view for explainingmain components of yet another preferred embodiment of the opticalconcentration measuring system that embodies the concentration measuringmethod of the present invention.

FIG. 10 is an explanatory schematic configuration view for explainingmain components of yet another preferred embodiment of the opticalconcentration measuring system that embodies the concentration measuringmethod of the present invention.

FIG. 11 is an explanatory schematic configuration view for explaining apreferred example of a differential signal forming portion adopted inthe present invention.

FIG. 12 is an explanatory schematic configuration view for explaininganother preferred example of the differential signal forming portionadopted in the present invention.

FIG. 13 is an explanatory schematic configuration view for explainingyet another preferred example of the differential signal forming portionadopted in the present invention.

FIG. 14 is an explanatory schematic configuration view for explainingyet another preferred example of the differential signal forming portionadopted in the present invention.

FIG. 15 is a graph showing a relationship between an absorbance valuemeasured with respect to a gas concentration and a value equivalent tothree times a standard deviation of a noise superimposed on the measuredsignal.

FIG. 16 is an outline external view illustrating an embodiment of a casein which the present invention is applied to a mobile terminal device.

FIG. 17 is a block diagram of an internal configuration of an embodimentin a case in which the present invention is applied to a mobile terminaldevice.

FIG. 18 is an explanatory schematic configuration view for explainingyet another preferred example of the differential signal forming portionadopted in the present invention.

FIG. 19 is an explanatory schematic configuration view for explainingmain components of yet another preferred embodiment of the opticalconcentration measuring system that embodies the concentration measuringmethod of the present invention.

FIG. 20 is an explanatory schematic configuration view for explainingmain components of yet another preferred embodiment of the opticalconcentration measuring system that embodies the concentration measuringmethod of the present invention.

FIG. 21 is a flowchart for explaining a preferred embodiment of theconcentration measuring method of the present invention.

FIG. 22 is a diagram illustrating the timing of a gas concentrationmeasuring step, light amount adjustment, and gas introductionillustrated in the flowchart in FIG. 21.

FIG. 23 is a timing chart of an ON/OFF state of light emission of eachlight source, and an output Vp of an integrating amplifier illustratedin the flowchart in FIG. 21.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a timing chart for explaining the principles of aconcentration measuring method of the present invention. In the presentinvention, a concentration measuring device for embodying theconcentration measuring method of the present invention is activated,and a signal of an absolute value of a background light in a space wherethe device is placed is read as a difference between outputs S20 and S10(absolute value output X).

Next, light from a light source 1 that emits light (Lλ1) having a firstwavelength is received by a light-receiving sensor, and a differentialoutput signal (GΔ1) of a difference between outputs S30 and S40 is read(output as a sum of the background light and the light of the lightsource 1).

Next, light from a light source 2 that emits a light (Lλ2) having asecond wavelength is received by the same light-receiving sensor, and adifferential output signal (GΔ2) of a difference between outputs S50 andS60 is read (output as a sum of the background light and the light ofthe light source 2).

Measurement data can be calibrated using the absolute value output X,even if a change occurs in an amount of light of the light source, anabsorbance of an object to be measured as a result of a temperaturechange, or the like.

With the light-receiving signals from the light sources 1, 2 output asdifferential output signals, noise of a circuit system can be removed,making it possible to achieve detection with high accuracy, even if theconcentration is weak.

In FIG. 1, “↑” indicates the output timing of the light-receivingsensor. While in principle the output timing “↑” includes a rise startpoint (t1) and a fall start point (t2) of the output of thelight-receiving sensor, the output timing “↑” in FIG. 1 is the timingbetween the rise start point (t1) and the fall start point (t2). This isbecause, when one measurement ends, an electronic circuit is partiallyreset for the next measurement. That is, a measurement period and areset period may overlap due to a time lag in the circuit and thus, toreliably avoid effects therefrom, the output timing “↑” is the timingbetween the rise start time (t1) and the fall start time (t2).

FIG. 2 is a block diagram of a configuration example of an opticalconcentration measuring system 100 serving as a preferred embodimentthat embodies the concentration measuring method of the presentinvention.

The optical concentration measuring system 100 comprises a light sourceportion 101, a light-focusing optical portion 102, a light-receivingsensor portion 106, a differential signal forming portion 108, a signalstorage/processing portion 110, a display unit 112, a control unit 113,and an operation portion 114.

The optical concentration measuring system 100 illustrated in FIG. 2comprises an optical gas concentration measuring sub-system 100-1 and acontrol/operation sub-system 100-2.

The optical gas concentration measuring sub-system 100-1 comprises anoptical gas concentration measuring device 100-3.

The optical concentration measuring sub-system 100-1 comprises the lightsource portion 101, the light-focusing optical portion 102, thelight-receiving sensor portion 106, the differential signal formingportion 108, the signal storage/processing portion 110, and the displayunit 112.

The control/operation sub-system 100-2 comprises the control unit 113and the operation portion 114.

An object 104 to be measured, subject to concentration measurement of apreferred chemical component, is arranged in a predetermined positionbetween the light-focusing optical portion 102 and the light-receivingsensor portion 106.

While the light source portion 101 illustrated in FIG. 2 comprises twolight sources including a light source 101 a that emits the light (Lλ1)having the first wavelength and a light source 101 b that emits thelight (Lλ2) having the second wavelength, the present invention is notlimited thereto, allowing a single light source that emits the light(Lλ1) having the first wavelength and the light (Lλ2) having the secondwavelength.

A light-emitting portion capable of irradiating light having two or moredifferent wavelengths such as described above may comprise two or morelight-emitting elements, each capable of irradiating light having onetype of wavelength. Furthermore, the light-emitting portion preferablycomprises at least one light-emitting element capable of irradiatinglight having two or more different wavelengths (multiple wavelengthlight-emitting element). This decreases the number of light-emittingelements arranged in the device interior, making it possible to reducethe size of the device.

When two light sources are adopted, disposing the two light sources asclose to each other as possible so that each light can be irradiated onsubstantially the same optical axis increases the accuracy of themeasured value, and is thus preferred.

When a single light source is adopted, the light (Lλ1) and the light(Lλ2) are selectively separated by means such as a wavelength selectingoptical filter prior to being irradiated onto the object 104 to bemeasured.

When the lights (Lλ1, Lλ2) having the two wavelengths are irradiatedusing a single light source, the device is designed so that the lighthaving the applicable wavelength is irradiated in accordance with anirradiation timing using an optical wavelength selecting filter such asa spectrum filter.

While the light (Lλ1) having the first wavelength and the light (Lλ2)having the second wavelength may each be light having a singlewavelength, adoption of light having multiple wavelengths, each having abandwidth for a wavelength, is preferred, taking into consideration easeof acquisition of the light source, such as an LED, and cost. Such lightpreferably has a center wavelength (wavelength with a peak intensity) ofλ1 or λ2.

In the present invention, the light (Lλ1) is light having a wavelengththat has an absorbability with respect to a chemical component subjectto concentration measurement. In contrast, the light (Lλ2) is a lighthaving a wavelength that has no or substantially no light absorbabilitywith respect to the chemical component, or an absorbability with respectto the chemical component that is relatively lower than that of thelight (Lλ1).

In the present invention, a light such as the light (Lλ2) is preferablyadopted since measurement accuracy increases when there is noabsorbability with respect to the chemical component or to the extentthe absorbability differs from that of the light (Lλ1).

When the concentrations of a plurality of chemical components aremeasured using the same object to be measured, the light (Lλ1) isprepared in a quantity equivalent to the number of chemical componentsto be measured. That is, given N as the number of chemical components,the light (Lλ1) is prepared in a quantity of n (Lλ1 n, where n is apositive integer). Among the lights (Lλ1 n, where n is a positiveinteger), the light selected as applicable is the light having awavelength or a wavelength range that exhibits an absorbability withrespect to the one chemical component only and no or substantially noabsorbability with respect to any other chemical component. For example,when glucose and hemoglobin are measured using the same object to bemeasured, light (Lλ11) that exhibits absorbability with respect toglucose but not with respect to hemoglobin, and light (Lλ12) that doesnot exhibit absorbability with respect to glucose but does with respectto hemoglobin are selected.

For the light (Lλ2), light that exhibits no or substantially noabsorbability with respect to either chemical component is selected.

As the light source of the light source portion, needless to say, alight source that emits light according to these conditions is selectedand used.

The light (Lλ1) and the light (Lλ2) are irradiated onto the object 104to be measured in accordance with a time-sharing method.

The light (Lλ1) and the light (Lλ2) are preferably irradiated onto thesame optical axis or substantially the same optical axis when irradiatedonto the object 104 to be measured. That is, even when a chemicalcomponent subject to concentration measurement has a spotteddistribution or an uneven distribution spatially or temporally in theobject 104 to be measured, when the positions in which the light (Lλ1)and the light (Lλ2) pass through the object 104 to be measured are thesame or substantially the same, the measurement period is, at the sametime, extremely short, resulting in the advantage of achieving a highlyaccurate measurement minimally affected by measurement errors.

An irradiated light 103 formed by the light (Lλ1) or the light (Lλ2) isirradiated onto the object 104 to be measured and, as a result, atransmitted light 105 exits from the exact opposite side of the object104 to be measured.

The transmitted light 105 enters a light-receiving surface of alight-receiving sensor located in the light-receiving sensor portion106.

The light-receiving sensor portion 106 outputs an electric signal 107 inresponse to the received light.

The signal 107 is either a signal 107 a based on the light (Lλ1) or asignal 107 b based on the light (Lλ2).

The signal 107 a and the signal 107 b are input to the differentialsignal forming portion 108 either sequentially based on a set timedifference or simultaneously.

When input based on a set time difference, the signal input first may,depending on the case, be held for a predetermined period in apredetermined circuit inside the differential signal forming portion 108in accordance with a timing for forming the differential signal.

A differential output signal 109 output from the differential signalforming portion 108 in accordance with the input of the signal 107 istransferred to the signal storage/processing portion 110 andstored/processed so as to output an output signal 111.

The output signal 111 is transferred to the display unit 112. Thedisplay unit 112 that received the output signal 111 displays aconcentration display of the measured chemical component on a displayscreen of the display unit 112 as a value corresponding to the outputsignal 111.

The above series of processes is controlled by the control unit 113 inaccordance with instructions from the operation portion 114.

The light-receiving sensor constituting the light-receiving sensorportion 106 may be a single element such as a photodiode, or a linesensor or area sensor in which a predetermined number of light-receivingpixels is one-dimensionally or two-dimensionally disposed, respectively.

When the chemical component to be measured is not uniform in the object104 to be measured, a measurement error resulting from positionaldependency may decrease the measurement accuracy, and thus adoption of aline sensor or an area sensor is preferred. In particular, adoption ofan area sensor that has a light-receiving surface having a size thatcovers an exiting surface from which the transmitted light 105 exits,orthogonal to the optical axis of the object 104 to be measured, cansignificantly increase measurement accuracy, and is thus preferred.

While the light (Lλ1) and the light (Lλ2) have each been described usinga light having a single wavelength, the wavelength is not necessarilylimited thereto in the present invention, and the wavelength may have abandwidth (wavelength range). That is, in the present invention, aluminous flux having a predetermined wavelength range may be used.

Next, an example of actual concentration measurement using the system100 of FIG. 2 will be described on the basis of FIGS. 3 and 4. FIG. 3 isa flowchart for explaining a preferred embodiment of the concentrationmeasuring method of the present invention.

When a button switch of the operation portion 114, or the like, forstarting measurement is pressed, concentration measurement is started(step 201).

In step 202, the existence or absence of the specimen 104 serving as theobject to be measured, including if the specimen 104 is appropriatelyplaced in a predetermined position, is determined. When it is determinedthat the specimen 104 has been appropriately placed, the first light(Lλ1) and the second light (Lλ2) necessary and appropriate for measuringthe concentration of a chemical component to be measured in the specimen104 are selected in step 202.

Selection of the first light (Lλ1) and the second light (Lλ2) is made bysetting the light source 101 a for the first light (Lλ1) and the lightsource 101 b for the second light (Lλ2) in predetermined positions inthe optical concentration measuring system 100, or dispersing the lightusing a spectroscope.

When selection is based on the establishment of a light source,selection of the first light (Lλ1) and the second light (Lλ2) can bemade in advance from an absorption spectrum of the chemical component tobe measured in the specimen 104, allowing step 203 to be performedbefore step 201.

Next, in step 204, acquisition of an analytical curve for deriving theconcentration value of the chemical component to be measured based onmeasurement data is started.

The analytical curve can be acquired by reading the data of ananalytical curve stored in advance in a storage portion of the opticalconcentration measuring system 100, or by creating a new analyticalcurve as described in FIG. 5.

Once acquisition of the analytical curve is complete, measurement of thespecimen 104 is started as indicated in step 206.

When measurement is started, the first light (Lλ1) and the second light(Lλ2) are irradiated onto the specimen 104 for a predetermined period bytime-sharing at a predetermined interval.

The first light (Lλ1) and the second light (Lλ2) that passed through thespecimen 104 are received by a light-receiving sensor set in thelight-receiving sensor portion 106 (step 207).

When the light-receiving sensor receives each transmitted light of thefirst light (Lλ1) and the second light (Lλ2) by time-sharing, an outputsignal of a size corresponding to the amount of received light is outputeach time light is received. In accordance with this output signal,“−log (1−ΔT)” is calculated (step 208).

Next, in step 209, whether or not “−log (1−ΔT)” is in the range of theanalytical curve is determined.

If “−log (1−ΔT)” is within the range of the analytical curve, theconcentration of the targeted chemical component in the specimen 104 isderived on the basis of the analytical curve data (step 210).

Next, in step 209, whether or not “−log (1−ΔT)” is in the range of theanalytical curve is determined.

If “−log (1−ΔT)” is within the range of the analytical curve, theconcentration of the targeted chemical component in the specimen 104 isderived on the basis of the analytical curve data (step 210).

FIG. 4 is a timing chart for explaining a signal output timing of theexample in FIG. 3. That is, FIG. 4 is a timing chart showing the timeresponses of an output OUT1 of the first light source 101 a, an outputOUT2 of the second light source 101 b, an output OUT3 of thelight-receiving sensor, an output OUT4 of the differential signal, and agas concentration GC.

Here, “output of the light source” is the amount of light emitted duringthe period that the light is on (hereinafter “ON period”) and, when thelight has high directivity, is substantially equivalent to the amount oflight received by the light-receiving sensor.

In the present invention, each light from the light sources 101 a, 101 bcan be focused by the light-focusing optical portion 102 as illustratedin FIG. 7 to 9, or a branch-type optical fiber 801 can be adopted asillustrated in FIG. 10, and thus as long as the light sources 101 a, 101b are arranged by bringing an emitting surface of the light sources 101a, 101 b near or in contact with an incident surface of thelight-focusing optical portion 102 or an incident surface of thebranch-type optical fiber 801, it is possible to make the amount oflight emitted during the ON period of each of the light sources 101 a,101 b close to or substantially equivalent to the amount of lightreceived by the light-receiving sensor.

The gas concentration GC can, for example, be measured as a change inconcentration of the target gas obtained by detecting an output signal(differential signal output OUT4) at timings T1 to T4 illustrated inFIG. 4 and deriving the value from the detected output signal value andthe analytical curve acquired in advance.

FIG. 4 illustrates a state of the gas concentration GC increasing instages over time.

When the output OUT1 of the first light source and the output OUT2 ofthe second light source are output on the same axis at mutuallypredetermined and repeated intervals at timings such as illustrated inFIG. 4, the gas to be measured does not exist before timing T1, and thusthe output OUT3 of the light-receiving sensor is output as pulses S11,S21 having the same size.

During the period between timings T1 and T2, the period between timingsT2 and T3, and the period between the timings T3 and T4, the pulses S12,S22, S13, S23, S14, S24 are output. While the sizes of the pulses S12,S13, S14 are the same as the size of the pulse S11, the sizes of thepulses S22, S23, S24 decrease in stages in accordance with the level oflight absorption of the gas to be measured.

That is, because the light from the second light source is absorbed inthe gas to be measured and the amount of light received by thelight-receiving sensor gradually decreases in accordance with the gasconcentration, the sizes of the pulses S22, S23, S24 decrease in stagesin accordance with the level of concentration of the gas to be measured.

FIG. 5 explains an example of a method for acquiring an analytical curvein advance, prior to measurement of the gas concentration. FIG. 5 is aflowchart for finding the analytical curve.

To acquire the analytical curve, an analytical curve acquiring device isused.

When acquisition of the analytical curve is started (step ST1), whetheror not an optical measuring cell has been prepared is determined in stepST2.

Once the optical measuring cell has been prepared, the flow proceeds tostep ST3. In step ST3, whether or not a predetermined carrier gas hasbeen introduced into the cell interior in a predetermined unit amount isdetermined.

When it is determined that the predetermined carrier gas has beenintroduced into the cell interior in a predetermined unit amount, theflow proceeds to step ST4.

This step of determining whether or not the carrier gas has beenintroduced may be omitted, or the step may be changed to a step fordetermining if the cell interior has reached a predetermined degree ofvacuum. This determination of whether the cell interior has reached apredetermined degree of vacuum may be omitted as well.

In either case, the cell interior needs to be cleaned before proceedingto step ST4 in order to acquire a more accurate analytical curve.

In step ST4, a plurality of gases subject to concentration measurementis sequentially introduced into the cell, and the absorbance of the gasof each concentration is measured.

Once measurement is completed, the flow proceeds to step ST5.

In step ST5, the analytical curve is created on the bases of theabsorbance measurement data.

FIG. 6 illustrates an example of an analytical curve created in thisway.

FIG. 6 is a graph showing a relationship between the gas concentrationGC and “−log (1−ΔT).”

Once the analytical curve is created, the flow can transition toconcentration measurement of the specimen.

Next, a preferred embodiment according to the present inventionillustrated in FIGS. 7 to 10 will be described. In FIGS. 7 to 10, thesame components as those in FIG. 2 will be denoted using the samereference numerals.

FIG. 7 is an explanatory schematic configuration view for explaining amain component 100 a of a preferred embodiment of the opticalconcentration measuring system that embodies the concentration measuringmethod of the present invention. FIG. 7 is an example of concentrationmeasurement by transmitted light.

In a main component 500, the light source portion comprises the firstlight source 101 a that emits the first light (Lλ1) and the second lightsource 101 b that emits the second light (Lλ2).

The first light (Lλ1) emitted from the first light source 101 a isfocused on the optical axis by the light-focusing optical portion 102,passed along the optical axis as an irradiated light 103 a, andirradiated onto the object 104 to be measured. The amount of theirradiated light 103 a not absorbed in the object 104 to be measuredexits the object 104 to be measured as a transmitted light 105 a.

The transmitted light 105 a enters the light-receiving surface of thelight-receiving sensor portion 106.

When the transmitted light 105 a is received by the light-receivingsensor portion 106, the electric signal 107 photoelectrically convertedin accordance with the amount of the transmitted light 105 a is outputfrom the light-receiving sensor portion 106.

The signal 107 output from the light-receiving sensor portion 106 isinput to the differential signal forming portion 108 configured by adifferential signal forming circuit.

The second light (Lλ2) emitted from the second light source 101 b ispassed along the optical axis as an irradiated light 103 b andirradiated onto the object 104 to be measured in the same way as thefirst light (Lλ1), and a transmitted light 105 b exits the object 104 tobe measured accordingly.

In the case of the second light (Lλ2), the light is either not absorbedin the object 104 to be measured, or absorbed with a low absorbabilitycompared to the first light (Lλ1). Thus, the amounts of the irradiatedlight 103 b and the transmitted light 105 b are either the same orsubstantially the same, or the difference thereof is less than thedifference between the irradiated light 103 a and the transmitted light105 a.

FIG. 8 is an explanatory schematic configuration view for explainingmain components of another preferred embodiment of the opticalconcentration measuring system that embodies the concentration measuringmethod of the present invention. Except for the fact that FIG. 8 is anexample of measurement by reflected light while FIG. 7 is an example ofmeasurement by transmitted light, the example in FIG. 8 is the same asthat in FIG. 7, and thus a detailed description thereof will be omitted.

FIG. 9 is an explanatory schematic configuration view for explainingmain components of yet another preferred embodiment of the opticalconcentration measuring system that embodies the concentration measuringmethod of the present invention.

Except for the fact that FIG. 9 is an example of measurement byscattered light while FIG. 7 is an example of measurement by transmittedlight, the example in FIG. 9 is the same as that in FIG. 7, and thus adetailed description thereof will be omitted.

FIG. 10 is an explanatory schematic configuration view for explaining amain component of yet another preferred embodiment of the opticalconcentration measuring system that embodies the concentration measuringmethod of the present invention. Except for the fact that FIG. 10 adoptsa branch-type optical fiber 801 for the light-focusing optical portion102 in the example in FIG. 7, the example in FIG. 10 is the same as thatin FIG. 7, and thus a detailed description thereof will be omitted.

FIG. 11 illustrates a circuit diagram for explaining a preferred exampleof the differential signal forming portion adopted in the presentinvention.

A differential signal forming portion 900 comprises a (charge)integrating amplifier 902, a sample/hold circuit 903, and a differentialamplifier 904.

When the transmitted light, reflected light, or scattered light producedupon irradiation of light having a predetermined wavelength forconcentration measurement onto the object 104 to be measured subject toconcentration measurement, such as a fruit or a vegetable, is receivedby a photodiode 901 for light reception, an electric signal P1corresponding to the amount of received light is output from thephotodiode 901. The electric signal P1 is input to the integratingamplifier 902.

The integrating amplifier 902 is provided for sensitivity enhancement soas to allow measurement down to subtle changes in gas concentration ofthe specimen 107.

The output signal of the integrating amplifier 902 is input to thesample/hold circuit 903.

A sampled/held analog signal is input to the differential amplifier 904.

Gas Concentration Measurement Example Embodying Present Invention

Next, an example that embodies the present invention will be describedusing a gas concentration measurement example.

A preferred embodiment of the concentration measuring method formeasuring concentration by using a plurality of lights having differentwavelengths and irradiating the plurality of lights by time-sharing willnow be described.

In the following, a preferred embodiment of a gas concentrationmeasurement example that uses transmitted light for measurement will beprimarily described.

Cases where reflected light or scattered light is used for measurementrather than transmitted light, needless to say, also fall into thecategory of the present invention, and are naturally within thetechnical field.

Further, the embodiment described below, needless to say, can be easilydeveloped even in a case where the concentration of a solution or thesugar content of a fruit or a vegetable is measured rather than theconcentration of a gas.

To embody the present invention as a gas concentration measuring device,the measuring device may comprise a regular light source, alight-receiving photodiode, electronic circuit components, and the likethat are easily acquirable, based on a premise of compatibility with themeasurement target, and thus in the following descriptions mattersobvious to persons skilled in the art will be omitted and main pointswill be simplified.

The specimen (object to be measured) is, for example, a gas that flowsthrough a gas pipe.

The gas pipe is provided with an incident surface into which light (ameasured light hλ) used for measurement enters, and an exiting surfacefrom which light, having passed through the gas pipe, exits to theoutside.

The incident surface and the exiting surface are made of a materialhaving a transmittance of “1” or substantially “1” with respect to themeasured light hλ.

Regardless of whether the gas that flows through the gas pipe is asingle type or a plurality of types of mixtures, the measuring devicecan measure the concentration of the target gas.

In the following, the case of the single type is described usingtrimethylgallium (TMGa), for example, as the gas serving as thespecimen.

Other examples of the specimen gas type include trimethylindium (TMIn)and titanium tetrachloride (TiCl4).

In the gas concentration measurement of trimethylgallium (TMGa), an LEDthat emits light (Lλ1) having a center light wavelength of 500 nm isadopted as the first light source 101 a, for example, and the lightintensity thereof is 1.0 mW/cm²/nm.

An LED that emits light (Lλ2) having a center light wavelength of 230 nmis adopted as the second light source 101 b, and the light intensitythereof is 1.0 mW/cm²/nm.

In the present invention, the light (Lλ1) 103 a emitted from the firstlight source 101 a and the light (Lλ2) 103 b emitted from the secondlight source 101 b are transmitted through the specimen 104 at separatetimes (by time-sharing), and enter the light-receiving sensor of thelight-receiving sensor portion 106. As the light-receiving sensor, aphotodiode (S1336-18BQ) manufactured by Hamamatsu Photonics K.K, forexample, may be used. The received light sensitivity of thelight-receiving sensor in this case is 0.26 A/W at a light wavelength of500 nm, and 0.13 A/W at a light wavelength of 230 mm.

The output signal 107 of the light-receiving sensor portion 106 is inputto the differential signal forming circuit 108, and the output signal109 is output from the differential signal forming circuit 108accordingly.

A light source that emits light having an absorbance that changesdepending on the concentration of the gas of the specimen 104, and alight source that emits light having an absorbance that does not orsubstantially does not change depending on the concentration of the gasof the specimen 104 are adopted as the first light source 101 a and thesecond light source 101 b, respectively.

While the above gas concentration measurement example has been describedusing the configuration in FIG. 7 that measures transmitted light,naturally the measurement can be applied to the configuration in FIG. 8that uses a reflected light and to the configuration in FIG. 9 that usesa scattered light without having to particularly re-describe thedetails.

Further, while an optical path of the first light source 101 a and anoptical path of the second light source 101 b differ in the object 104to be measured if the light-focusing optical portion 102 does not existin the configuration illustrated in FIG. 7, preferably the first lightsource 101 a and the second light source 101 b are arranged as close toeach other as possible so as to bring the optical paths as close to thesame optical path as possible.

Or, the optical paths can be made substantially identical when thebranch-type optical fiber 801 is adopted as illustrated in FIG. 10 inplace of the light-focusing optical portion 102, and thus adoption ofthe branch-type optical fiber 801 is preferred.

FIG. 11 is a configuration diagram for explaining a configuration of apreferred example of the differential signal forming circuit.

The differential signal forming circuit 900 illustrated in FIG. 11 isprovided with the (charge) integrating amplifier 902 to increasesensitivity so that subtle changes in the gas concentration of thespecimen 107 can be measured.

The output signal of the (charge) integrating amplifier 902 is input tothe sample/hold circuit 903.

A sampled/held analog signal is input to an analog-digital converter(ADC) 1301.

An optical signal based on the first light source, an optical signalbased on the second light source, and a differential signal betweenthese two signals are output from the ADC 1301.

FIG. 4 is a timing chart showing the time responses of the output OUT1of the first light source 101 a, the output OUT2 of the second lightsource 101 b, the output OUT3 of the light-receiving sensor, the outputOUT4 of the differential signal, and the gas concentration GC, and thisis as previously described.

Here, “output of the light source” is the amount of light emitted duringthe ON period and, when the light has high directivity, is substantiallyequivalent to the amount of light received by the light-receivingsensor.

In the present invention, the light from the light sources 101 a, 101 bcan be focused by the light-focusing optical portion 102 as illustratedin FIG. 7 to 9, or the branch-type optical fiber 801 can be adopted asillustrated in FIG. 10, and thus as long as the light sources 101 a, 101b are arranged by bringing the emitting surface of the light sources 101a, 101 b near or in contact with the incident surface of thelight-focusing optical portion 102 or the incident surface of thebranch-type optical fiber 801, it is possible to make the amount oflight emitted during the ON period of the light sources 101 a, 101 bclose to or substantially equivalent to the amount of light received bythe light-receiving sensor.

In general, absorbance is given based on the following formula:

[Formula 1]

−log(I/I ₀)=−log(1−ΔT)=αK  (1)

Here, “I₀” indicates the intensity of the incident light, “I” indicatesthe intensity of the transmitted light, and “K” indicates the gasconcentration. α is a coefficient and is determined by an optical pathlength in the specimen 104, a light absorption coefficient of the gassubject to concentration measurement in the specimen 104, and the like.

Further, “ΔT” indicates the absorbance difference. In this embodiment,the optical path lengths are set so that a is substantially 0 for thefirst light source 101 a, and 2.18×10−4/ppm for the second light source101 b. Given “I₁” as the intensity of the transmitted light of the light(Lλ1) emitted from the first light source 101 a and “I₂” as theintensity of the transmitted light of the light (Lλ2) emitted from thesecond light source 101 b, formula (1) can be modified to formula (2)when I₁ uses the fact that the transmittance difference with respect tothe optical wavelength of the first light source, regardless of gasconcentration, is substantially 0.

[Formula 2]

$\begin{matrix}{{{- \log}\mspace{11mu} \left( {l - {\Delta \; T}} \right)} = {{{- \log}\mspace{11mu} \left( {1 - \frac{X}{I_{1}}} \right)} = {\alpha \; K}}} & (2)\end{matrix}$

Here, “X” is the output value of the differential signal, and isequivalent to “I₂-I₁.”

According to this formula, the absorbance of the specimen 104 can bemeasured with high accuracy using the output OUT1 of the first lightsource 101 a having an absorptivity that changes in accordance with thegas concentration, and the output OUT2 of the second light source 101 bhaving an absorptivity that does not change in accordance with the gasconcentration.

Thus, there is no need to measure gas concentrations to create ananalytical curve for each measurement using known reference samples.

A gas densitometer can measure changes in absorptivity in a stablemanner, even if there are changes in the measurement system, gastemperature, or the like.

Setup is performed so that an integrated charge (1) of the integratingamplifier 902 based on the first light source 101 a and the integratingcharge (2) of the integrating amplifier 902 based on the second lightsource 101 b when the gas concentration is “0” are equal orsubstantially equal.

Here, in this embodiment, an integration period (1) during output of thefirst light source 101 a and an integration period (2) during output ofthe second light source 101 b were adjusted so that the charges were6.1×10−9 C.

The integration period (1) and the integration period (2) of thisembodiment were set to 4.0 msec and 2.0 msec, respectively.

FIG. 15 shows a relationship between an absorbance value measured withrespect to a gas concentration and a value equivalent to three times astandard deviation of a noise superimposed on the measured signal atthis time.

Further, when measurement was made using this charge, the main noisecomponent was confirmed as photon shot noise.

Based on the results, when the charge value is 6.1×10−9 C, the effect ofthe photon shot noise proportional to the square root of the signalcharge became relatively small, making it possible to measure anabsorbance difference ΔT up to 5×10−5 with 99% reliability. That is, thegas concentration could be measured to an accuracy of 0.1 ppm.

Further, according to the embodiment of the present invention, output isobtained from a difference between signals based on two lights havingdifferent wavelengths, even if the temperature changes, making itpossible to cancel an amount of fluctuation in a transmittance thatchanges according to temperature. Thus, even if there is temperaturefluctuation during measurement, stable sensitivity can be achieved withhigh accuracy.

In the present invention, a communication module for short-rangecommunication, such as WiFi, Bluetooth (registered trademark), or NearField Communications (NFC), or a communication module for satellitecommunication is incorporated in the concentration measuring device thatembodies the present invention, making it possible to make theconcentration measuring device function as an information terminaldevice on a network. For example, a patient in a hospital can measurehis or her blood sugar level in the hospital bed using a non-invasivetype of concentration measuring device according to the presentinvention when it is time for measurement or when instructed by thenurse station, and send the measurement data as is to the nurse station.This makes it possible to alleviate the labor burden of a nurse in termsof making hospital room visits for each patient and taking measurements.

Furthermore, while, for example, a person at risk for diabetes, a personwith a low or high blood sugar level being observed and treated at home,or the like may experience an abnormality in blood sugar level whiledriving a vehicle, become light-headed, no longer be able to drive orfind it difficult to drive normally, and cause an accident, such aperson can wear a non-invasive type concentration measuring device thatcomprises a communication function according to the present inventionand have the device perform measurements while he or she is driving. Insuch a case, the device can detect an abnormality in blood sugar level,immediately send the signal indicating abnormality detection to thevehicle that the person is driving, and automatically stop the vehiclein a prompt manner or automatically guide the vehicle to a safe areasuch as the side of the road and stop the vehicle. Moreover, carriedinsulin can then be administered and recovery to normalcy achieved.

Further, the data of the abnormal detection can be automatically sentalong with necessary personal data of the driver to a family doctor ornearby hospital to request emergency instructions from the hospital.

While FIG. 11 illustrates a preferred example of the differential signalforming circuit in the realization of the present invention, the presentinvention is not limited thereto, allowing adoption of the differentialsignal forming circuits illustrated in FIGS. 12 to 14 as preferredexamples as well.

In FIGS. 12 to 14, components that fulfill the same functions as thosedenoted with the reference numerals in FIG. 11 are denoted using thesame reference numerals as FIG. 11.

The configuration illustrated in FIG. 12 is the same as that in FIG. 11except that, in addition to a circuit for a differential signal output905, a circuit for a pre-differential signal output 1001 has been added.

With the addition of the circuit for the pre-differential signal output1001, there is the advantage that, compared to the configurationillustrated in FIG. 11, even if fluctuation occurs in the absolute valueof absorbance due to temperature change or the like, or temporalfluctuation occurs in the light output of the light source, the amountof these fluctuations can be measured and calibrated.

In the configuration illustrated in FIG. 13, two systems for signaltransmission (sample/hold circuits 903 a, 903 b→differential amplifiers904 a, 904 b) and the ADC 1301 are further provided compared to theconfiguration illustrated in FIG. 12.

This configuration results in the advantage of being able to eliminatethe offset of the integrating amplifier compared to that in FIG. 12.

FIG. 14 is an example of a circuit designed in more detail than theexample in FIG. 13.

In FIG. 14, an integrating (accumulation) amplifier portion 1401, whichis similar to the integrating amplifier 902, and a 1/10× amplifierportion 1402 are provided. In addition, the differential amplifierportions 904 a, 904 b are each provided with two instrumentationamplifiers for differential output.

Such a configuration results in the advantage of being able to eliminatethe offset of the differential amplifiers.

Next, an embodiment of a preferred example of an electronic devicecomprising the concentration measuring function according to the presentinvention will be described.

FIGS. 16 and 17 are outline configuration views illustrating anembodiment when the present invention is applied to a mobile terminaldevice.

FIG. 16 is an outline external view, and FIG. 17 is a block diagram ofthe internal configuration.

A mobile terminal device 1701 illustrated in FIGS. 16 and 17 comprises aglobal positioning system (GPS) positioning portion 1703, a calculationprocessing portion 1704, a storage device 1705, and a display unit 1706.

When the device does not require GPS positioning, the GPS positioningportion 1703 is omitted.

Further, the device may comprise the GPS positioning portion 1703, andan acceleration sensor 1708 and an angular velocity sensor 1709 may beomitted.

Examples of the mobile terminal device 1701 include a mobile electronicdevice such as a mobile telephone device having a navigation function, apersonal digital assistant (PDA), a tablet, or a mobile PC, awristwatch, and a wearable article such as a scouter, a necklace, aring, or a bracelet having an electronic device function.

Examples of the mobile terminal device 1701 further include a mobilebarometer or altimeter for mountain climbing, and a stopwatch.

The mobile terminal device 1701 is capable of intercommunicating with adevice equipped with a transceiver function such as a transceiver base,a transceiver satellite, a NAVI system mounted to a vehicle, a handheldNAVI device, a transceiver connected to a private network system, orother mobile terminal device.

Description is given in the following using the example of a transceiversatellite 1702 as an example of a device equipped with a transceiverfunction.

The GPS positioning portion 1703 functions as a first current positioncalculating portion that receives a position information signal sentfrom the transceiver satellite 1702 and identifies a current position.

The calculation processing portion 1704 receives detection signals ofthe vertical acceleration sensor 1708 that detects a number of steps andthe angular velocity sensor 1709 that detects a direction, autonomouslyidentifies the current position based on these, and executes navigationprocessing.

The calculation processing portion 1704 comprises a microcomputer, acentral processing unit (CPU), and the like.

The storage device 1705 comprises a ROM 1705 a that stores a processingprogram executed by the calculation processing portion 1704 and stores astorage table required in calculation processing, a RAM 1705 b thatstores calculation results and the like required in calculationprocessing, and a non-volatile memory 1705 c that stores the currentposition information when navigation processing ends.

The display unit 1706 displays navigation image information output fromthe calculation processing portion 1704, and comprises a liquid crystaldisplay unit, an organic EL display unit, or the like.

A clock portion 1707 displays a year, month, day, and time correctedusing the current time information that indicates the year, month, day,and time output from the GPS positioning portion 1703 when the GPSpositioning portion 1703 is activated.

The calculation processing portion 1704 receives the current positioninformation output from the GPS positioning portion 1703, the currenttime information that indicates the year, month, day, and time outputfrom the clock portion 1707, the acceleration information output fromthe acceleration sensor 1708 mounted on a hip position of the user thatretains the mobile terminal device 1701, the angular velocityinformation corresponding to the direction of the walking by the userand output from the angular velocity sensor 1709, such as a gyroscope,mounted to the mobile terminal device 1701, and concentrationmeasurement information from a concentration measuring portion 1710according to the present invention.

The concentration measuring portion 1710 comprises the opticalconcentration measuring system illustrated in FIG. 7 to 10 or an opticalconcentration measuring device comprising the same functions as thesystem, and may be detachably mounted to the mobile terminal device 1701main body or integrally configured with the main body.

When the concentration measuring portion 1710 is detachably mounted tothe main body, the concentration measuring portion 1710 can be removedfrom the main body at the time of measurement and, for example, broughtinto contact with the body of a person, allowing measurement of thesugar level in the blood, for example.

The concentration measuring portion 1710 and the main body are bothprovided with a communication module for short-range communication, suchas Wifi, Bluetooth (registered trademark), or NFC, making it possible toperform communication between the concentration measuring portion 1710and the main body even when the concentration measuring portion 1710 isremoved from the main body.

According to the mobile terminal device 1701, concentration measurementdata, position information data, and specific individual data stored inthe storage device 1705 can be sent to a transmission destination. Forexample, when an abnormality arises in the blood sugar level of a personwhile driving a vehicle, a signal indicating the abnormality is sent tothe vehicle, causing the vehicle to automatically stop and, at the sametime, the concentration measurement data, the position information data,and specific individual data is sent to a family doctor or a hospital inwhich the family doctor is located, making it possible to requestinstructions for appropriate treatment from the doctor and, in somecases, promptly dispatch an emergency vehicle.

A communication portion 1711 that performs wireless communication withan external wireless communication device is connected to thecalculation processing portion 1704.

The ROM 1705 a stores a storage table of position information by region.

Additionally, the ROM 1705 a stores an autonomous positioningcalculation program for performing autonomous positioning calculations,and a calculation portion selection processing program for selectingeither current position information calculated by the GPS positioningportion 1703 or current position information calculated by theautonomous positioning calculation processing performed by theautonomous positioning program.

The storage table of position information by region charts the names ofprefectures across the country, the seat names of governments of eachprefecture, and the latitude (N) and the longitude (E) of each seat ofgovernment.

The calculation processing portion 1704 executes the autonomouspositioning calculation processing in accordance with the autonomouspositioning calculation program that performs autonomous positioningcalculations.

This autonomous positioning calculation processing is started whenautonomous calculation processing is selected by the calculation portionselection processing and, once the previous current position identifiedby the GPS positioning portion 1703 is set as the initial position inthe initial state, is executed as timer interrupt processing everypredetermined time period (10 msec, for example) with respect to apredetermined main program.

That is, first the autonomous positioning calculation processing readsan angular velocity θv detected by the angular velocity sensor 1709,then integrates the angular velocity θv, calculates the direction θ, andtransitions to the next step.

In the next step, the autonomous positioning calculation processingreads a vertical acceleration G detected by the acceleration sensor1708, calculates a number of steps P from a change pattern of thevertical acceleration G, multiplies a pace width W set in advance by thecalculated number of steps P to calculate a moved distance L, updatesthe current position information on the basis of the calculateddirection θ and the moved distance L, displays the updated currentposition information on the display unit 1706 over map information, endsthe timer interrupt processing, and returns to the predetermined mainprogram.

Furthermore, the calculation processing portion 1704 executescalculation portion selection processing that selects either the currentposition information identified by the GPS positioning portion 1703 inaccordance with the calculation portion selection processing program orthe current position information identified by the autonomouspositioning calculation processing.

According to this calculation portion selection processing, execution isstarted when the navigation processing is selected on the mobileterminal device 1701 after power ON.

Examples of the mobile terminal device 1701 include a mobile electronicdevice such as a mobile telephone device having a navigation function, apersonal digital assistant (PDA), a tablet, or a mobile PC, awristwatch, and a wearable article such as a scouter, a necklace, aring, or a bracelet having an electronic device function.

While in the examples heretofore formation of the differential signalhas been exemplified by formation via an electric circuit (hardware)such as a differential circuit and a differential amplification circuit,the present invention is not limited thereto, allowing formation usingsoftware of digital calculation processing.

An example of a preferred embodiment will be described using FIG. 18.

The embodiment illustrated in FIG. 18 comprises a differential signalforming portion 1800 and a light-receiving sensor portion 1801.

The differential signal forming portion 1800 comprises an integratedcircuit portion 1802, an analog-digital converting (A/D converting)portion (ADC) 1803, and a differential signal forming element portion1804.

The light-receiving sensor portion 1801 is provided with a photodiode1805 as a light-receiving sensor for measurement. The integrated circuitportion 1802 is provided with an operational amplifier 1806, a capacitorC1, and a switch SW1.

While the example of the differential signal forming portion 900illustrated in FIG. 11 forms the differential signal 905 using an analogsignal, a differential signal 1809 in the example illustrated in FIG. 18is formed by performing digital calculation processing afteranalog-digital conversion (A/D conversion) of a signal 1807 output fromthe integrated circuit portion 1802.

An output terminal of the photodiode 1805 is electrically connected withan inverting input pin of the operational amplifier 1806.

The non-inverting pin of the operational amplifier 1806 is grounded.

Between the integrated circuit portion 1802 and the ADC 1803, a switchSW2 is provided as necessary and a signal transmission path is formed.The signal transmission path can be formed by electrically connectingthe area between the integrated circuit portion 1802 and the ADC 1803.

When two lights (a first light and a second light) differing inwavelength or wavelength band are sequentially irradiated bytime-sharing onto an object (specimen) to be measured, the first lightand the second light that pass through the object to be measured aresequentially received by the photodiode 1805 by time-sharing inaccordance with the irradiation.

When the photodiode 1805 receives the light, an optical charge isproduced, and the optical charge is accumulated in the capacitor C1. Asignal 1807 of a voltage of a size corresponding to this accumulatedcharge is output from the integrated circuit portion 1802 when theswitch SW2 is turned ON. The signal 1807 is input to the analog-digitalconversion means (ADC) 1803, converted into a digital signal, and outputfrom the ADC 1803 as a signal 1808. The digitized signal 1808 is inputto the differential signal forming element portion 1804.

Either a signal 1808 a corresponding to the first light or a signal 1808b corresponding to a second light, whichever is input first, istemporarily saved in the differential signal forming element portion1804 interior at least until the signal to be subsequently input isinput.

When the signals 1808 a, 1808 b respectively corresponding to the firstlight and the second light to be measured are sequentially input to thedifferential signal forming element portion 1804, differential signalformation processing is implemented in the differential signal formingelement portion 1804 on the basis of these signals 1808 a, 1808 b, andthe differential signal 1809 is output from the differential signalforming element portion 1804.

However, when a plurality of light sources is used as the light sourcefor emitting lights having different wavelengths as in the examples inFIGS. 7, 8, 9, and 10, the amount of light may change independently overtime for each light source.

This change in the amount of light over time for each light source isnot substantial as long as appropriate light sources are selected, andthus generally does not affect the concentration measurement.

However, selecting the light sources requires time and effort, andincreases the cost of the product.

Further, in the case of gas concentration measurement or the like,sediment may accumulate on an inner wall surface of a light-receivingwindow or an inner wall surface of a light-exiting window of a gas flowpath arranged in the measured optical path, or each of these inner wallsurfaces may become contaminated and, when the amount of transmittedlight changes over time, a change may occur in differential output overtime even if gas of the same concentration is introduced into the gasflow path, making it no longer possible to achieve an accurateconcentration measurement.

In the following, a method that eliminates such concerns and, if timevariability occurs in each amount of light of the plurality of lightsources, eliminates the effects on concentration measurement isdescribed.

FIG. 19 illustrates an example of such a preferred embodiment.

The embodiment in FIG. 19 is similar to the embodiment in FIG. 10, butfurther comprises a microcomputer 1901.

Thus, components that are the same as those in FIG. 10 will be denotedusing the same reference numerals, and duplicate descriptions thereofwill be omitted.

In a gas concentration measuring system 1900, the signal 109 output fromthe differential signal forming portion 108 is sent to an informingportion 1902 comprising audio output means, display means, and the like,and the informing portion 1902 externally provides information based onthe signal 109 by audio, a display, or the like.

The differential signal forming portion 108 and a light source drivingportion 1903 are controlled by the microcomputer 1901.

The microcomputer 1901 controls the light source driving portion 1903 sothat light emission amounts of light sources 101 a, 101 b areappropriate in accordance with the differential signal formed by thedifferential signal forming portion 108.

This control is performed each time a differential signal is formed, anda feedback (FB) signal 1904 output from the light source driving portion1903 is input to the light source portion 101.

The light emission amounts of the light sources 101 a, 101 b arecontrolled in accordance with this FB signal 1904.

In this way, even if the light emission amounts of the light sources 101a, 101 b change over time, the light emission amounts are instantlycontrolled so as to be appropriate.

Further, even if the transmitted amount of light transmitted through ameasurement cell changes due to unforeseen circumstances (such ascontamination of the light-receiving window or light-exiting window ofthe cell), it is possible to appropriately perform condensationmeasurement.

Another embodiment is illustrated using FIGS. 20 to 23.

The embodiment in FIG. 20 is similar to the embodiment in FIG. 12, butfurther comprises an analog-digital converter (ADC) 2004 and amicrocomputer 2005.

Thus, components that are the same as those in FIG. 12 will be denotedusing the same reference numerals, and duplicate descriptions thereofwill be omitted.

In a concentration measuring system 2000, the differential output 905output from the differential amplifier 904 is input to the ADC 2004 byactivation of a switch SW5.

The differential output 905 input to the ADC 2004 is subjected to A/Dconversion inside the ADC 2004. As a result, an output 2009 is outputfrom the ADC 2004 and sent to an informing portion 2007, and information(such as the gas concentration value, for example) based on the output2009 is provided.

The photodiode 901 receives the measured light that passes through aconcentration measurement cell portion 1900 a illustrated in FIG. 19,for example.

A microcomputer 2005 issues an instruction signal for adjusting thelight emission amount, the integration time of the amount of receivedlight, and the timing of the switches SW1 to SW5 on the basis of thedifferential output 905 or the output 2009.

When the light emission amount of the light source is adjusted, amicrocomputer 2005 sends an instruction signal to a light source drivingportion 2006. The light source driving portion 2006 that receives thisinstruction signal controls a light source portion (not illustrated) sothat the light emission amount becomes a predetermined amount inaccordance with the instruction signal.

Further, the instruction signal from the microcomputer 2005 may be sentto an integrating amplifier portion 2002, and the ON/OFF timing of theswitch SW1 may be controlled to adjust an accumulation time of thecapacitor C1 (integration time adjustment of the amount of receivedlight).

Furthermore, the concentration measurement accuracy can be optimized bysending the instruction signal from the microcomputer 2005 to adifferential signal forming portion 2001 and adjusting the ON/OFF timingof the switches SW2 to SW5.

Naturally, at this time, overall optimization of the concentrationmeasuring system 2000 can be achieved and measurement accuracy can befurther increased by simultaneously sending the instruction signal fromthe microcomputer 2005 to the integrating amplifier portion 2002 andcontrolling the ON/OFF timing of the switch SW1 to adjust theaccumulation time of the capacitor C1.

Next, a general overview of the steps for measuring concentration usingthe gas concentration measuring system 2000 in FIG. 20 will bedescribed.

To make the description easy to understand, the description will begiven using the concentration measurement of gas as an example forconvenience sake.

While the light used includes two lights having different absorbanceswith respect to the gas subject to concentration measurement, thedescription will be given with one light as a light not absorbed by thegas subject to concentration measurement.

(1) Adjusting the Light Amount of the Light Source

(1-1) A gas, such as Ar or N2, that does not absorb the used light isintroduced into a gas concentration measurement cell for measuring theconcentration of a predetermined gas.(1-2) A differential output V0=Vp (λ2)−Vp (λ1) based on the lightamounts of the light sources having the optical wavelengths λ1 and λ2 ismeasured using a time-sharing method.

Here, LEDs having different optical wavelengths are used as the lightsources. The output Vp of the integrating amplifier 902 is expressed bythe formula Vp=(Ipd×tint)/C1. Here, Ipd indicates the photodiode (PD)current, tint indicates the integration time of the integratingamplifier, and C1 indicates the capacity at which the feedback of theintegrating amplifier is applied.

(1-3) The light emission amount or light integrated amount is adjusted(referred to as light adjustment) so that the differential output of thelights having different wavelengths is a predetermined value or less.

In FIG. 20, the light emission amount of each light source is adjustedto a predetermined value by, for example, sending the instruction signalfrom the microcomputer 2005 to the light source driving portion 2006.

Here, “predetermined value” refers to the value obtained by subtractingan estimated value of a maximum output differential resulting ofspecimen gas (the gas subject to concentration measurement) from amaximum range of differential output determined by circuit conditions ofthe differential signal forming portion 2001.

Using the microcomputer 2005, a voltage (PD driving voltage) for drivingthe photodiode (PD) 901 is adjusted by sending a feedback (FB) signal tothe light source driving portion 2006 in accordance with thedifferential output 905.

Or, the integration times tint1 and tint2 of the integrating amplifier902 are adjusted by sending the FB signal to the integrating amplifierportion 2002 in accordance with the differential output 905.

Or, both the PD driving voltage and the integration times of theintegrating amplifier 902 may be adjusted.

(1-4) The differential output value V0 after light adjustment is storedin storage means such as semiconductor memory such as RAM (DRAM, ARAM)or ROM, a HDD, or the like. The stored differential output value V0 isread as needed and utilized to calculate concentration when theconcentration of the specimen gas is measured.(1-5) While adjustment of the light amount is executed during theinitial period of concentration measurement, adjustment may be performedwith every subsequent measurement or intermittently.

(2) Example of Specimen Gas Concentration Measurement

(2-1) Specimen gas is introduced into the gas concentration measurementcell.(2-2) The differential output V (t) is obtained by the time-sharingconcentration measuring method of the present invention.(2-3) V0 is subtracted from V (t) to obtain the differential outputchange amount Vc (t) corresponding to the concentration of the specimengas.

Vc(t)=V(t)−V0

(2-4) The absorbance is obtained from Vc (t).

A detailed flow of the steps for measuring gas concentration isillustrated in FIG. 21.

Next, an example of actual concentration measurement using the system2000 of FIG. 20 will be described on the basis of FIGS. 21 to 24. Forconvenience sake, the concentration measurement cell portion 1900 aillustrated in FIG. 19 is used as the concentration measurement cellportion. For each of explanation, the light source portion 101illustrated in FIG. 19 is used as the light source portion.

FIG. 21 is a flowchart for explaining a preferred embodiment of theconcentration measuring method of the present invention.

FIG. 21 is similar to the flowchart in FIG. 3, and thus steps having thesame meanings as those in FIG. 3 are described using the same referencenumerals as FIG. 3.

When a button switch of an operation portion similar to the operationportion 114, or the like, for starting measurement is pressed,concentration measurement is started (step 201).

In step 202, the existence or absence of the specimen 104, including ifthe object (specimen/concentration measurement cell) 104 to be measuredis appropriately placed in a predetermined position, is determined. Whenit is determined that the specimen 104 has been appropriately placed,the first light (Lλ1) and the second light (Lλ2) necessary andappropriate for measuring the concentration of a chemical component tobe measured in the specimen 104 are selected in step 202.

Selection of the first light (Lλ1) and the second light (Lλ2) is made bysetting the light source 101 a for the first light (Lλ1) and the lightsource 101 b for the second light (Lλ2) in predetermined positions inthe optical concentration measuring system 100, or dispersing the lightusing a spectroscope.

When selection is based on the establishment of a light source,selection of the first light (Lλ1) and the second light (Lλ2) can bemade in advance from an absorption spectrum of the chemical component tobe measured in the specimen 104, allowing step 203 to be performedbefore step 201.

Next, in step 204, acquisition of an analytical curve for deriving theconcentration value of the chemical component to be measured based onmeasurement data is started.

The analytical curve can be acquired by reading the data of ananalytical curve stored in advance in a storage portion of the opticalconcentration measuring system 100, or by creating a new analyticalcurve as described in FIG. 5.

Once acquisition of the analytical curve is complete, measurement of thespecimen 104 is started as indicated in step 206.

When measurement is started, introduction of a non-absorbable gas, suchas argon (Ar), into the specimen 104 is started (step 2100).Subsequently, adjustment of the light amount as previously described isstarted (step 2101). Once completion of light amount adjustment isverified (step 2102), the flow proceeds to the next step 2103.

When completion of light amount adjustment is confirmed, introduction ofthe specimen gas that includes the gas component subject to chemicalconcentration measurement (gas subject to concentration measurement)into the specimen 104 is started (step 2103).

At the stage when at least the specimen gas has been filled in thespecimen 104, the first light (Lλ1) and the second light (Lλ2) areirradiated for a predetermined period onto the specimen 104 bytime-sharing at a predetermined interval (part of step 207).

The first light (Lλ1) and the second light (Lλ2) that passed through thespecimen 104 are received by a light-receiving sensor (PD 901) set in alight-receiving sensor portion similar to the light-receiving sensorportion 106 illustrated in FIG. 1 (part of step 207).

Next, whether or not output of the light-receiving sensor (PD 901) iswithin the measurement range is confirmed (step 2104). When output ofthe light-receiving sensor (PD 901) is confirmed to be within themeasurement range, the flow proceeds to step 208.

When output of the light-receiving sensor (PD 901) is not within themeasurement range (when “NO”), the flow returns to step 2100 and theprocess of step 2100 below is executed.

When the light-receiving sensor (PD 901) receives each transmitted lightof the first light (Lλ1) and the second light (Lλ2) by time-sharing, anoutput signal of a size corresponding to the amount of received light isoutput each time light is received. In accordance with this outputsignal, “−log (1−ΔT)” is calculated (step 208).

Next, in step 209, whether or not “−log (1−ΔT)” is in the range of theanalytical curve is determined.

If “−log (1−ΔT)” is within the range of the analytical curve, theconcentration of the targeted chemical component in the specimen 104 isderived on the basis of the analytical curve data (step 210).

FIG. 22 is a diagram illustrating an example of the timing of the gasconcentration measuring step, light amount adjustment, and gasintroduction illustrated in the flowchart in FIG. 21.

FIG. 23 is a timing chart of the ON/OFF state of light emission of eachlight source, and the output Vp of the integrating amplifier illustratedin the flowchart in FIG. 21.

The symbols in FIG. 23 have the following meanings:

(a) Gas: Non-absorbable gas (Ar), optical wavelength: λ2

(b) Gas: Non-absorbable gas (Ar), optical wavelength: λ1

(c) Gas: Specimen gas, optical wavelength: λ2

(d) Gas: Specimen gas, optical wavelength: λ1

(e) Gas: Specimen gas, optical wavelength: λ2

(f) Gas: Specimen gas, optical wavelength: λ1

-   -   Integrating amplifier output: Vp=(Ipd×tint)/C1    -   Ipd: PD current    -   tint: Integrating time    -   C1: Capacity of the integrating amplifier portion 2002, feedback        of the accumulation time adjustment is applied.

“Output of the light source” in the present invention is the amount oflight emitted during the ON period and, when the light has highdirectivity, is substantially equivalent to the amount of light receivedby the light-receiving sensor.

While the above has been described as a preferred embodiment of thepresent invention using FIGS. 20 to 23, it is understood thatsignificant amount of the content described in FIGS. 1 to 18 isundeniably applicable to the example described using FIGS. 20 to 23.

For example, the steps can be performed in accordance with the flowchartillustrated in FIG. 5 utilizing an analytical curve acquiring device toacquire the analytical curve.

In the embodiment of the present invention described using FIGS. 19 to23, the following advantages are expected:

(1) Even if the initial differential output is not zero, gasconcentration can be measured with high accuracy.(2) Differential output is monitored in real time and feedback controlis performed, making it possible to measure gas concentration with highaccuracy even if the characteristics of the LED (light source) and thetransmittance of the optical path change over time.

While the above explanation has been described two types of lights formeasurement that have different wavelengths and are irradiated on theobject to be measured, the present invention is not limited thereto,allowing three types or more. This point is easily understood by thoseskilled in the art.

As described above, the concentration measuring method of the presentinvention has universality, i.e., the ability to be embodied in variousforms and modes.

DESCRIPTIONS OF REFERENCE NUMERALS

-   100 Optical concentration measuring system-   100-1 Optical concentration measuring sub-system-   100-2 Control/Operation sub-system-   100-3 Optical concentration measuring device-   101 Light source portion-   101 a, 101 b Light source-   102 Light-focusing optical portion-   103, 103 a, 103 b Irradiated light-   104 Object to be measured-   105, 105 a, 105 b Transmitted light-   106 Light-receiving sensor portion-   107, 107 a, 107 b Electric signal-   108 Differential signal forming portion-   109 Differential output signal-   110 Signal storage/processing portion-   111 Output signal-   112 Display unit-   113 Control unit-   114 Operation portion-   201 to 211 Step-   500, 600, 700, 800 Optical gas concentration measuring system-   801 Branch-type optical fiber-   801 a, 801 b Branch optical path-   802 a, 802 b Irradiated light-   900, 1000, 1300, 1400 Differential signal forming portion (circuit    configuration)-   901 Photodiode-   902 Integrating amplifier-   903, 903 a, 903 b Sample/Hold circuit-   940, 904 a, 904 b Differential amplifier-   905 Differential signal output-   906 Pre-differential signal output-   1101 Differential signal forming element portion-   1301 ADC-   1302 Signal output-   1401 Integrating amplifier portion-   1402 1/10× integrating amplifier portion-   1701 Mobile terminal device-   1703 GPS positioning portion-   1704 Calculation processing portion-   1705 Storage device-   1706 Display unit-   1708 Acceleration sensor-   1709 Angular velocity sensor-   1800 Differential signal forming portion-   1801 Light-receiving sensor portion-   1802 Integrated circuit portion-   1803 Digital-analog converting portion-   1804 Differential signal forming element portion-   1805 Photodiode-   1806 Operational amplifier-   1807, 1808 Signal-   1809 Differential signal-   Lλ1 Light having a first wavelength-   Lλ2 Light having a second wavelength 1900, 2000 Gas concentration    measuring system-   1900 a Concentration measurement cell portion-   1901, 2005 Microcomputer-   1902 Informing portion-   1903, 2006 Light source driving portion-   2001 Differential signal forming portion-   2002 Integrating amplifier portion-   2003 Signal selecting and differential amplifier portion-   2004 ADC

1. A concentration measuring method for optically measuring aconcentration of a predetermined chemical component in an object to bemeasured, the method comprising the steps of: irradiating at least light(1) having a first wavelength (λ1) that has an absorbability withrespect to the chemical component, and light (2) having a secondwavelength (λ2) that has no or substantially no absorbability withrespect to the chemical component, or an absorbability that isrelatively lower than that of the light (1), from light-emitting unittoward the object to be measured using a time-sharing method;sequentially receiving the light that is produced by the irradiation andpasses through the object to be measured by light-receiving unit;inputting a first light-receiving signal (1) based on the light (1) anda second light-receiving signal (2) based on the light (2), eachproduced by the received light into differential signal forming unit;deriving the concentration of the predetermined chemical component froma measured value based on a differential signal output from thedifferential signal forming unit in accordance with the input, and datastored in storage unit in advance; and feeding back a feedback signalcorresponding to the differential signal to light emission amountcontrol unit for controlling a light emission amount of thelight-emitting unit and/or the differential signal forming unit.
 2. Aconcentration measuring method for optically measuring a concentrationof a predetermined chemical component in an object to be measured, themethod comprising the steps of: irradiating at least light having afirst wavelength that has an absorbability with respect to the chemicalcomponent, and light having a second wavelength that has no orsubstantially no absorbability with respect to the chemical component,or an absorbability that is relatively lower than that of the lighthaving the first wavelength, from a single light-emitting unit towardthe object to be measured using a time-sharing method; sequentiallyreceiving the light that is produced by the irradiation and passesthrough the object to be measured in a time-sharing manner by a singlelight-receiving unit; inputting a first light-receiving signal based onthe light having the first wavelength and a second light-receivingsignal based on the light having the second wavelength, each produced bythe received light, into differential signal forming unit; deriving theconcentration of the predetermined chemical component from a measuredvalue based on an output signal output from the differential signalforming unit in accordance with the input, and data stored in storageunit in advance; and controlling a light emission amount of thelight-emitting unit on the basis of a feedback signal corresponding tothe differential signal.
 3. A concentration measuring method foroptically measuring a concentration of a predetermined chemicalcomponent in an object to be measured, the method comprising the stepsof: irradiating at least light having a first wavelength that has anabsorbability with respect to the chemical component, and light having asecond wavelength that has no or substantially no absorbability withrespect to the chemical component, or an absorbability that isrelatively lower than that of the light having the first wavelength,from a single light-emitting unit toward the object to be measured usinga time-sharing method; sequentially receiving the light that is producedby the irradiation and passes through the object to be measured by asingle light-receiving unit; inputting a first light-receiving signalbased on the light having the first wavelength and a secondlight-receiving signal based on the light having the second wavelength,each produced by the received light, into differential signal formingunit; and deriving the concentration of the predetermined chemicalcomponent from a measured value based on an output signal output fromthe differential signal forming unit in accordance with the input, anddata stored in storage unit in advance.
 4. A concentration measuringmethod, comprising the steps of: irradiating at least light having afirst wavelength and light having a second wavelength, each having adifferent light absorptivity with respect to an object to be measured,onto the object to be measured using a time-sharing method; sequentiallyreceiving the light of each wavelength that optically passes through theobject to be measured as a result of the irradiation of the light ofeach wavelength, using a common light-receiving sensor; forming adifferential signal between a signal related to the light having thefirst wavelength and a signal related to the light having the secondwavelength output from the light-receiving sensor in accordance with thereceived light; deriving a concentration of a chemical component in theobject to be measured on the basis of the differential signal; andcontrolling the amount of light during the emission of at least one ofthe light having the first wavelength and the light having the secondwavelength on the basis of a feedback signal corresponding to thedifferential signal.
 5. The concentration measuring method according toclaim 1, wherein the object to be measured is in a gas state.
 6. Theconcentration measuring method according claim 1, wherein the object tobe measured is in a liquid state.
 7. The concentration measuring methodaccording to claim 1, wherein the object to be measured is a fruit or avegetable.
 8. The concentration measuring method according to claim 1,wherein the light-emitting unit comprises a light source that emits thelight having the first wavelength and a light source that emits thelight having the second wavelength.
 9. The concentration measuringmethod according to claim 1, wherein the light-emitting unit comprises alight source that emits the light having the first wavelength and thelight having the second wavelength.
 10. A concentration measuringmethod, comprising the steps of: irradiating at least a first light anda second light, each having a different light absorptivity with respectto an object to be measured, onto the object to be measured using atime-sharing method; receiving each light that optically passes throughthe object to be measured by irradiation of each light onto the objectto be measured, using a common light-receiving sensor; forming adifferential signal on the basis of a signal related to the first lightand a signal related to the second light output from the light-receivingsensor in accordance with the received light; and deriving aconcentration of a predetermined chemical component in the object to bemeasured on the basis of the differential signal.
 11. A concentrationmeasuring method, comprising the steps of: irradiating at least a firstlight and a second light, each having a different light absorptivitywith respect to an object to be measured, onto the object to be measuredusing a time-sharing method; receiving each light that optically passesthrough the object to be measured by irradiation of each light onto theobject to be measured, using a common light-receiving sensor; forming adifferential signal on the basis of a signal related to the first lightand a signal related to the second light output from the light-receivingsensor in accordance with the received light; deriving a concentrationof a predetermined chemical component in the object to be measured onthe basis of the differential signal; and controlling the amount oflight during the emission of at least one of the light having the firstwavelength and the light having the second wavelength on the basis of afeedback signal corresponding to the differential signal.
 12. Theconcentration measuring method according to claim 9, wherein irradiationusing the time-sharing method is performed by propagating the lightthrough irradiation optical paths in which the optical axes of theemitted light and received light are the same or substantially the same.13. A concentration measuring method, comprising the steps of:irradiating at least light having a first wavelength and light having asecond wavelength, each having a different light absorptivity withrespect to an object to be measured, onto the object to be measuredusing a time-sharing method; receiving the light of each wavelength thatoptically passes through the object to be measured as a result of theirradiation of the light of each wavelength, using a commonlight-receiving sensor; forming a differential signal between a signalrelated to the light having the first wavelength and a signal related tothe light having the second wavelength output from the light-receivingsensor in accordance with the received light; and deriving aconcentration of a chemical component in the object to be measured onthe basis of the differential signal.
 14. A concentration measuringmethod, comprising the steps of: irradiating at least light having afirst wavelength and light having a second wavelength, each having adifferent light absorptivity with respect to an object to be measured,onto the object to be measured using a time-sharing method; receivingthe light of each wavelength that optically passes through the object tobe measured as a result of the irradiation of the light of eachwavelength, using a common light-receiving sensor; forming adifferential signal between a signal related to the light having thefirst wavelength and a signal related to the light having the secondwavelength output from the light-receiving sensor in accordance with thereceived light; deriving a concentration of a chemical component in theobject to be measured on the basis of the differential signal; andcontrolling the amount of light during the emission of at least one ofthe light having the first wavelength and the light having the secondwavelength on the basis of a feedback signal corresponding to thedifferential signal.
 15. A concentration measuring method, comprisingthe steps of: irradiating at least a first light and a second light,each having a different light absorptivity with respect to an object tobe measured, onto the object to be measured using a time-sharing method;receiving each light that optically passes through the object to bemeasured by irradiation of each light onto the object to be measured,using a common light-receiving sensor; forming a differential signal onthe basis of a signal related to the first light and a signal related tothe second light output from the light-receiving sensor in accordancewith the received light; and deriving a concentration of a predeterminedchemical component in the object to be measured on the basis of thedifferential signal.
 16. A concentration measuring method, comprisingthe steps of: irradiating at least a first light and a second light,each having a different light absorptivity with respect to an object tobe measured, onto the object to be measured using a time-sharing method;receiving each light that optically passes through the object to bemeasured by irradiation of each light onto the object to be measured,using a common light-receiving sensor; forming a differential signal onthe basis of a signal related to the first light and a signal related tothe second light output from the light-receiving sensor in accordancewith the received light; deriving a concentration of a predeterminedchemical component in the object to be measured on the basis of thedifferential signal; and controlling the amount of light during theemission of at least one of the light having the first wavelength andthe light having the second wavelength on the basis of a feedback signalcorresponding to the differential signal.